Crystallization of lithium disilicate-based multicomponent glasses – effect of silica/lithia ratio

Soares, Roque S.; Monteiro, Regina da Conceição Corredeira; Lima, Maria Luísa; Silva, R.J.C.

doi:10.1016/j.ceramint.2014.08.074

Cited by 38 publications

(27 citation statements)

References 38 publications

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“…A smaller free energy of nucleation at small cluster radius for the LS phase is also observed in our simulations, but since none of the two methods investigates the reactive pathway and the kinetics associated to an eventual crystalline phase transition from the LS to LS 2 , explicitly, it is difficult to make speculation on the phase transformation. Both our results and those by McKenzie et al 40 are in good agreement with the facts experimentally measured by Differential Thermal Analysis (DTA) and SEM observations by Soares et al 29 . In fact, the DTA data has shown that two exothermic peaks appear at 615–680 °C and 750–800 °C, and these peaks are associated with the crystallization of the LS and LS 2 phases, respectively, by XRD measurement.…”

Section: Resultssupporting

confidence: 93%

“…The former would appear homogeneously from the bulk, whereas the latter can heterogeneously nucleate only on the glass surface where favorable exogenous conditions are present. Therefore, the failure of CNT in predicting the magnitude of the steady state nucleation rate is not due to the formation of metastable phases as suggested in some of earlier investigations [27][28][29] .…”

Section: Discussionmentioning

confidence: 81%

“…23 ). Meanwhile, others have obtained the LS crystalline phase 27 – 29 although the conversion of the LS crystal (if formed before) to the LS 2 crystal would require a high energetic cost because the two phases have quite different stoichiometry and structures, as shown in Fig. 1 (LS 2 has a double-layered silica structure with Li ions in the interlayers, whereas LS has a chain-like silica structure surrounded by Li ions).…”

Section: Introductionmentioning

confidence: 99%

“…A typical homogeneous crystallization is observed in the lithium silicate glass system close to the Li 2 O•2SiO 2 (lithium disilicate, LS 2 ) composition 7 , and many experimental investigations using a large variety of techniques [22][23][24][25][26][27][28][29] have been investigated. Accordingly, two possible phase evolution mechanisms have been proposed 7,28,29 : (1) both LS 2 and metastable Li 2 O•SiO 2 (lithium metasilicate, LS) phases simultaneously nucleate homogeneously but the latter phase disappears during the heat treatment or (2) the LS crystal is firstly nucleated and subsequently promotes the heterogeneous LS 2 crystal on it. The latter hypothesis was suggested by the fact that the CNT underestimates the steady-state nucleation rate in several orders of magnitude.…”

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confidence: 99%

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Disclosing crystal nucleation mechanism in lithium disilicate glass through molecular dynamics simulations and free-energy calculations

Lodesani

Menziani

Maeda³

et al. 2020

Sci Rep

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Unraveling detailed mechanism of crystal nucleation from amorphous materials is challenging for both experimental and theoretical approaches. In this study, we have examined two methods to understand the initial stage of crystal precipitation from lithium disilicate glasses using molecular dynamics simulations. One of the methods is a modified exploring method to find structurally similar crystalline clusters in the glass models, enabling us to find three different embryos, such as Li2Si2O5 (LS2), Li2SiO3 (LS) and Li3PO4 (LP), in the 33Li2O·66SiO2·1P2O5 glass (LS2P1), in which P2O5 is added as a nucleating agent. Interestingly, LS2 and LP crystals were found inside the LS2P1 glass while LS crystal appeared on the glass surface, which agrees with experimental observations. The other method is free energy calculation using a subnano-scale spherical crystal embedded in the glass model. This method, which we called Free-Energy Seeding Method (FESM), allows us to evaluate free energy change as a function of crystal radius and to identify critical size of the crystal precipitation. The free energy profiles for LS and LS2 crystal nuclei in the LS2 glass models possess maximum energy at a critical radius as expected by classical nucleation theory. Furthermore, the critical radius and the energy barrier height agree well with recent experimental investigation, proving the applicability of this method to design glass–ceramics by atomistic modeling.

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Section: Resultssupporting

confidence: 93%

Section: Discussionmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Disclosing crystal nucleation mechanism in lithium disilicate glass through molecular dynamics simulations and free-energy calculations

Lodesani

Menziani

Maeda³

et al. 2020

Sci Rep

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“…An n value of ~3 suggests bulk or three-dimensional crystal growth, whereas values close to 1 suggest surface nucleation and growth [57]. In this study, we found that the Avrami index of the glasses varied in the range of 2.6-4 and gradually increased with increasing nitrogen content of the glass.…”

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confidence: 57%

Crystallization pathways and some properties of lithium disilicate oxynitride glasses

Singh

Rodrigues

Orsolini

et al. 2017

Ceramics International

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Lithium silicates have been used as model glasses for scientific and technological studies of glass-ceramics because they easily crystallize in the interiors, even without the addition of any nucleating agent. On the other hand, partial replacement of oxygens with nitrogens affects most properties of oxide glasses, but its effect on the crystallization kinetics of the glasses has been poorly documented. In this work, we report, for the first time, on the crystallization kinetics of nitrited lithium silicate glasses. The oxynitride glasses were prepared by partial substitution of oxygen by nitrogen, up to 6 at.% N/(N+O), by melt-quenching the liquid under N 2 atmosphere inside a glove box. As expected, the density, microhardness, and Young's modulus of the glasses improved with increasing nitrogen content. Higher values of glass transition and crystallization peak temperatures were also obtained with an increase in the nitrogen content. Rietveld refinement analysis after adequate thermal treatment revealed that addition of nitrogen led to increasingly higher contents of lithium metasilicate at the expense of the (expected) lithium disilicate crystal phase. Crystallization kinetic parameters such as the activation energy and 2 Avrami index were calculated using Ozawa's equations. These two parameters also increased with increasing nitrogen content, whereas the crystal growth rates decreased with increasing nitrogen content. The above-described changes in the properties of the oxynitride glasses are straightforwardly explained by the increase in the connectivity of the glass network, which results in enhancement of the atomic packing density owing to partial substitution of twocoordinated oxygens by three-coordinated nitrogens.

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Effects of Surface Orientation and Termination Plane on Glass‐to‐Crystal Transformation of Lithium Disilicate by Molecular Dynamics Simulations

Sun

Dierolf

Jain

2020

Physica Status Solidi (b)

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Glass‐to‐crystal transformation of lithium disilicate is studied using molecular dynamics simulations using an effective partial charge potential. The structural evolution of the interface between glassy and crystalline lithium disilicate is analyzed to simulate crystallization of glass on pre‐existing crystal seeds. Besides previously used atomic number density, the distribution of Qn species (Si tetrahedra with n bridging oxygen) is shown to be an effective parameter for following this transformation quantitatively. The early stages of crystal growth are significantly affected by the orientation and termination of the surface of adjacent crystal, as indicated by calculated atomic density, partial ordering, atomic segregation, and an increase in Q3 concentration. In particular, under‐coordinated Si within the outer crystal layer is found to be most effective in transforming the amorphous structure toward crystallinity. The increase in Q3 in the glass close to interface region most clearly shows the initial stage of lithium disilicate crystal growth.

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Crystallization of lithium disilicate-based multicomponent glasses – effect of silica/lithia ratio

Cited by 38 publications

References 38 publications

Disclosing crystal nucleation mechanism in lithium disilicate glass through molecular dynamics simulations and free-energy calculations

Disclosing crystal nucleation mechanism in lithium disilicate glass through molecular dynamics simulations and free-energy calculations

Crystallization pathways and some properties of lithium disilicate oxynitride glasses

Effects of Surface Orientation and Termination Plane on Glass‐to‐Crystal Transformation of Lithium Disilicate by Molecular Dynamics Simulations

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